In most Space Opera settings space travel is commonplace and routine, but in some settings there are people who spend almost their entire lives in space. These people were born and raised on a starship or space station and can't imagine living on a planet. Often they act as traders, with an extended family owning and operating a ship. Recently, with knowledge of the ill effects of extended periods in space, Spacers are increasingly portrayed as genetically engineered subspecies that do not experience muscular and skeletal degeneration from zero-gravity, are immune to radiation, have prehensile toes...